Description: (Applicant's Description) The VCC Flow Cytometry Shared Resource provides state-of-the-art analytical flow cytometry capabilities to Cancer Center researchers. It features a Coulter EPICS XL four-color analytical flow cytometer equipped with an automated carousel loader, and two computer workstations for data acquisition and analysis. In its current configuration, the flow cytometer is capable of simultaneously collecting data from up to eleven different parameters in parallel. The facility has trained staff and expert scientists who can provide guidance with experimental design, development and application of new techniques or reagents, and help in interpreting and analyzing data. The facility is directed by Dr. James Koh and has one staff person, Mr. Scott Tighe. Two-tiered services are available, including either 1) operator-assisted runs or 2) unassisted runs for researchers or their designees who have had appropriate training from facility staff. This is a new VCC-run facility that was established and run in 1999 because of an expressed need by VCC researchers, particularly in support of groups studying cancer-related growth control, apoptosis, and cell-cycle regulation. An independent institutional FACS core offering sorting capabilities is available to VCC researchers but we do not propose it for CCSG support. This is the first request for CCSG support for a VCC Flow Cytometry.